Packages of Spice are said to be being thrown over the prison walls at arranged times for the inmates Getty

Prison staff at a jail in Kent have undergone hospital treatment after being affected by smoke from a so-called legal high used by the inmates. Four staff at HMP Rochester have been sent home and at least one has been hospitalised because of the second hand fumes from the drug Spice.

Spice, a synthetic cannabis which is said to be 100 times stronger than the Class B drug, has been routinely used by prisoners across the UK as it is relatively cheap and almost undetectable by testing equipment such as urine samples or drug hounds.

The use of Spice inside the prison is said to be "rife", according to reports, with packages being thrown over the prison walls at arranged times. A source close to the jail told Kent Online: "The staff are having one hell of a problem with this particular legal high.

"There was an incident where the fumes were so great they affected staff, including one who had a heart condition."

Spice, is said to give users a hallucinogenic experience but can also cause increased heart rates, seizures, psychosis, kidney failure and strokes. The substance was said to be factors in at least 19 prisoner deaths in the UK between 2012 and 2014, according to a report by Prisons and Probation Ombudsman (PPO) in 2015.

Nigel Newcomen, the ombudsman, said at the time: "The use of new psychoactive substances is a source of increasing concern, not least in prison. As these substances are not allowed in prison, and also because they are difficult to test for, it is possible that there are additional cases of prisoners who had used such drugs before their death."

A Prison Service spokesman said: "Governors use sniffer dogs, cell searches and drugs tests to find drugs in prison and punish those responsible. HMP Rochester staff are also working with police to restrict the supply of drugs. We have passed laws so that those smuggling packages over prison walls, including drugs, face up to two years in prison.

"However, it is clear more must be done, which is why the Justice Secretary has asked the Ministry of Justice to look at how we can ensure prisons have the right tools in place to tackle this kind of problem."